Entrepreneurship is defi ned as detecting and pursuing future opportunities (Shane & Venkataraman, 2000 ). Future opportunities are usually developed in the context of high uncertainty and complexity. Because of the uncertainty and complexity inherent in entrepreneurship, there has been great skepticism towards planning in entrepreneurship. As a matter of fact, one could even talk of a common stereotype that both researchers of entrepreneurship and entrepreneurs themselves perceive that planning is not helpful for entrepreneurs and that it may even backfi re (Baker, Miner, & Eesley, 2003 ; Honig & Karlsson, 2004 ; Sarasvathy, 2001 ). We think that this stereotype exists because it is easy to misunderstand the multifactorial functions of planning for entrepreneurship. Planning has multifactorial functions because planning can be done at diff erent levels (i.e. the individual, the team, or the organization) and planning can be formal or informal. Formal planning may be in the form of a business plan (often done by one entrepreneur) or in the form of a strategic plan (often developed as a longer exercise of bottom-up and top-down planning by a strategic department as a staff function for the CEO). Informal plans are usually in the head of the planner(s) and they are usually more concerned with detailing specifi c actions relevant for goal accomplishment. The various functions of planning may have advantages and disadvantages for entrepreneurship. Therefore, a comprehensive perspective on planning in entrepreneurship is necessary. In this chapter, we seek to present such a comprehensive perspective. We fi rst discuss the potential disadvantages and advantages of planning. We emphasize that it is important to consider the diff erent levels and the diff erent degrees of formality to better understand the positive and negative eff ects of planning discussed in the literature. We then present a theory of planning that helps us to better understand planning in entrepreneurship. In our discussion, we focus on the individual entrepreneur (or a small group of entrepreneurs) because entrepreneurial fi rms are often highly aff ected by an individual and the process of starting a fi rm and growing it is highly dependent upon the lead entrepreneur. Thus, the following discussion is centered mainly around the entrepreneur or a small group of founders or top managers of a fi rm (if not otherwise noted).